Hydraulic Machine Provided with a Direction Changing Drawer

The invention relates to hydraulic machines.

Known from document FR-3 024 503 is a hydraulic machine comprising a casing, radial pistons, a multilobe cam and a distributor. The machine comprises several submotors. A displacement selection slide valve is mounted sliding between a first position associated with a first displacement and a second position associated with a second displacement. The slide valve position control therefore allows choosing the displacement of the machine. The slide valve is coaxial with the machine and is located in the distributor.

A direction changing slide valve is also provided, which is mounted sliding between first and second positions associated with two pressure configurations. This slide valve is controlled by the pressure difference at the terminals of the machine. It allows, when the configuration of the motor is changed (i.e. when the low pressure and the high pressure are reversed), being certain that the submotor that is overridden or bypassed has no grooves fed at the high pressure. This direction changing slide valve forms in fact a slide valve for selecting the lowest of pressures. This second slide valve extends inside the first, coaxially with the latter. It should be remembered that, in the term “direction changing slide valve,” it is not always the direction of rotation of the hydraulic machine that is changed, but in fact the direction of the torque exerted on the shaft by the hydraulic machine. In fact, different configurations of the slide valve can be imagined where, while the shaft of the machine is turning in the same direction, the machine can operate either as a pump or as a motor (that is for example the case when the hydraulic motor is used in the pump mode to carry out hydrostatic braking).

However, this arrangement makes the manufacture of the machine more complex. It is possible to attempt a remedy by miniaturizing the direction changing slide valve, but this reduction in dimensions makes manufacture more costly and has its limits. In fact, the two slide valves must occupy a certain volume to avoid internal leakage between the lines of the high-pressure and low-pressure circuits. A certain quantity of matter must therefore be associated with them or a certain quantity of materials and great accuracy in the production of the parts in question.

One object of the invention is to facilitate the production of a hydraulic machine comprising such slide valves.

To this end, a hydraulic machine is provided according to the invention comprising:

Thus, by means of these positions of the direction changing slide valve, the constraints linked to bulk are reduced, which facilitates manufacture. It is then possible to easily produce a high-performance two displacement machine. The positions provided for the direction changing slide valve do not impact performance.

The displacement selection slide valve sees a large flow rate pass, in particular when the machine is in low displacement, given that recirculation of the fluid from the part of the machine that is overridden or bypassed occurs. On the other hand, the direction changing slide valve does not see a flow pass once it is locked in one of the two operating positions (aside from a leakage flow which is minimized by enlarging this slide valve).

The invention allows, if necessary, keeping the displacement selecting slide valve at the center of the distributor so that the circulation of the fluid occurs there as close as possible to the grooves of the high and low pressure lines. But it leads to keeping the direction change slide valve away from the axis of rotation. In the case where the latter extends outside the displacement selection slide valve, this simplifies its manufacture, given that the direction changing slide valve does not see a large flow rate of fluid pass.

Compared to the prior art, the fact of having two separate slide valves allows having slide valves less constrained to compactness.

This technology is applicable to all hydraulic machines, whether they are used in motor mode or in pump mode.

Again, in the term “direction changing slide valve,” it is not always the direction of rotation of the hydraulic machine that is changed, but actually the direction of the torque exerted on the shaft by the machine. In fact there exist different configurations of the slide valve where, when the shaft turns in the same direction, the machine can operate either as a pump or as a motor (this is for example the case when the motor is used in pump mode to carry out hydrostatic braking).

In one embodiment, the displacement selection slide valve extends within the distributor.

Given that the slide valve sees a large flow rate pass when the machine is in low displacement (recirculation of the fluid from the submotor is bypassed); this configuration shortens the trajectories of the oil in order to limit head losses.

It can be provided that the displacement selection slide valve is coaxial with the axis of rotation.

Again, given that the displacement selection slide valve sees a large flow rate pass when the machine is in low displacement (i.e. when one of the submachines is bypassed), this axial configuration shortens as much as possible the trajectories of the oil and limits head losses to a minimum.

It is possible to provide that the direction changing slide valve extends outside the displacement selection slide valve.

It can be provided that the direction changing slide valve is mounted sliding in a direction parallel to the axis of rotation.

It can also be provided that the direction changing slide valve is mounted sliding in a direction that is not parallel to the axis of rotation.

It can be provided that the machine comprises a high-pressure line and a low-pressure line and is configured so that the direction changing slide valve moves under the influence of a pressure in the high-pressure line. The hydraulic machine functions only if a pressure difference is established at its terminals. Depending on the “terminal” where the high pressure occurs, the slide valve places itself in one configuration or in another. The direction changing slide valve places itself in a recess which includes a chamber at each end, each chamber being respectively connected to one or the other of the high-pressure and low-pressure lines.

It can be provided that, the second displacement being less than the first displacement, the second displacement is implemented by a group of pistons or lobes of a cam, the group forming a regular polygon centered on the axis of rotation.

It is also possible to provide that the group forms a figure having axial symmetry and/or central symmetry.

Thus, the appearance of parasitic forces and moments is avoided.

Also provided according to the invention is a subassembly for a hydraulic machine,

The direction changing slide valve being mounted sliding along an axis distant from the axis of rotation.

For example, the displacement selection slide valve is coaxial with the main axis.

It can be provided that a fluid path from an inlet of the machine to the displacement changing slide valve is shorter than a fluid path from the inlet to the direction changing slide valve.

It can also be provided that,

Also provided according to the invention is a device comprising at least one machine according to the invention.

Also provided according to the invention is a method for controlling a hydraulic machine, in which:

Also provided according to the invention is a method of controlling a hydraulic machine, in which:

The direction changing slide valve being moved depending on whether it is the feed or the discharge duct where the high pressure is established in the machine,

We will describe a first embodiment of the hydraulic machine of the invention with reference to.

We are mainly presenting the aspects of the machinewhich relate to the invention. Supplementary details of the machine, known per se, could be obtained from document FR-3 024 503, already mentioned.

With reference to, the machinecomprises a fixed casing, in this case in three parts.,.and., succeeding one another along the axis of rotationand assembled for example by screws (not shown in the section plane). It comprises a corrugated or multilobe reaction camrigidly bonded to the central part.of the casing, and for example produced within it. The lobes of the cam are visible in.

The machine comprises a cylinder blockmounted in rotation relative to the casing and to the camaround the main axisand which has a plurality of cylindrical recesses, radial in the present example, able to be fed with fluid under pressure and inside which pistonsare mounted sliding. In this case, the cylinder blockdrives in rotation a shaftwhich cooperates for this purpose with splines (not shown) of the cylinder block. In this example, this shaft carries an output flange. Each pistoncarries a followerby means of which it is supported on the cam and rolls on it.

The machineis of the fixed casing type and has a rotating cylinder block. But the invention also applies to a machine with a rotating casing and a fixed cylinder block. The machinecan operate as a motor or as a pump.

As illustrated in, the machinecomprises an internal distributorwhich is bonded to the casing.,.,.with respect to rotation around the axis. In other words, the distributorand the camdo not turn relative to one another. The distributoris housed inside the rear part.of the casing, which is also designated here by the term “distribution cover.” This part.can be a single block by having the shape of a bell as illustrated in, or be closed at its axial end opposite to the cylinder block by an applied plate. This end is considered here to be the rear part of the machine and the flangeas its front part.

The distributorhas the function of feeding fluid under pressure to the recesses of the pistons when the machine operates in motor mode. The pressure of the pistons on the cam drives, given its multilobed shape, the rotation of the shaftrelative to the casing and therefore the driving of the load by the flange. In pump mode, the rotation of the shaft drives the rolling of the followerson the camand the reciprocation of the pistons in their recesses. This causes the discharge of fluid from these recesses and the pressurizing of the high-pressure line via the distributor.

The distributorhas a planar outer front faceextending in a plane perpendicular to the axisand into which the distribution ductsopen. These ducts extend in particular in a direction parallel to the axis.

The distributor also has an outer circumferential lateral facewhich has four annular circular groovesA,B,CetD. The grooves succeed one another in that order in the direction of the axisbetween the cylinder block, to which the grooveA is closest and the rear end, to which the grooveD is closest (closest to the rear end).

The distribution cover.has an inner lateral facewhich forms a cavity housing the distributorso that the two facesandface one another and are in contact with one another in a male-female assembly. The faceof the distribution cover has annular circular main groovesA,B,C andD, respectively facing groovesA,B,C andD of the distributor.

The groovesB andD communicate with main feed and discharge ducts, respectively R and L, which are bored into the wall of the distribution cover.. Ducts R and L, and therefore the high-and low-pressure lines, are connected to a hydraulic circuit. In a preferred direction that is selected arbitrarily for the description, the fluid feed in forward movement is accomplished through the duct L and the grooveD, while discharge occurs through the duct R and the grooveB. Conversely, in reverse, feed is accomplished through the duct R and the grooveB while discharge occurs through the duct L and the grooveD.

Referring to, the distributorhas a cylindrical central recesswith axis. Here the recess is of the through type and opens at the two ends of the distributor. Nevertheless, on the cylinder block side there is a plate for retaining the spring.

Annular groovesB,A,C andD are provided in the inner face of this recess, succeeding one another in that order along the front and rear axis.

These grooves are open in their zone directed toward the axis while opening into the central recess. They are spaced from one another along the axis so that they are not contiguous. The grooves form with the ductsfour respective enclosures for the fluid, which we designate here with the same reference symbolsB,A,C andD as the grooves.

Here the machine has two active operating displacements. For this purpose, the ductsform two respective assemblies each comprising a first group of ducts and a second group of ducts. All the ductsallow feeding the piston recessesand are provided in the distributor.

In a first assembly, the first group of ductsis connected to the first enclosureB. Here these ductsare four in number and form the diagonals of a rectangle as illustrated in. The second group of ducts is connected to a secondD of the enclosures. Here these ducts are also four in number and form the diagonals of a rectangle identical to the previous one but offset angularly relative to it around the axis. These two groups form a main submachine.

In the second assembly, the first group of ducts is connected to a third of the enclosuresA. Here the ducts are two in number and are diametrically opposed on either side of the axis. The second group of ducts is connected to the fourth enclosureC. Here the ducts are also two in number and diametrically opposed on either side of the axis, this diameter being angularly offset relative to the previous one around the axis. These two groups form a secondary submachine which is sometimes bypassed or overridden so as to make the machine operate with the smallest displacement, namely only with the main submachine.

For example, each submotor or submachine corresponds to a distribution of a certain number of lobes or to a row of pistons of the cylinder block.